Microwave heating is a well known technique for rapidly cooking or reheating an item, e.g. food, by using microwaves. In a microwave oven, the microwave energy is provided by a microwave source, usually a magnetron, and then fed to a cavity for heating the item. A microwave oven comprising a magnetron (e.g. a magnetron powered with a “regular” mains high voltage transformer or an inverter-powered magnetron) normally includes a high-voltage transformer for driving the microwave source. Further, cooling of the microwave source is normally necessary for the output power of the microwave source to be maximal since, under operation, heat is generated by the microwave source.
In household microwave ovens, the cooling system is usually based on forced air generated by a fan and guided to the magnetron via various forms of air channels. Prior art cooling systems are often static in that the motor of the cooling system is run at a constant speed throughout an operation cycle. The cooling level of the cooling system is normally determined by identifying the operating scenario that requires a specific airflow through the magnetron (the cooling system being usually designed using the so called normal test, wherein the cooling is optimized for a 1000 g water load). The cooling system is then set at the highest cooling level required for the particular operating scenario. Drawbacks of prior art cooling systems for microwave ovens are that a rather high level of noise is produced and that the energy consumption is not optimized.